Linear actuator with ex-zone 1 rated housing

ABSTRACT

A linear actuator assembly that can include an electric motor contained in an explosive (EX) certifiable housing, a linear actuator external to the EX certifiable housing, the linear actuator coupled to and driven by the electric motor, the linear actuator having a first axis and a body, and a piston of the linear actuator that extends or retracts relative to the body when the linear actuator is driven by the electric motor, the piston having a second axis, with the first axis and the second axis being parallel and spaced apart. The electrically operated linear actuator assembly can provide up to 700 kN clamping force when engaging a tubular. A plurality of the linear actuator assemblies can provide up to 250 kNm of torsional force to a tubular string joint when used in a wrench assembly.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. § 119(e) to U.S. patent application Ser. No. 62/991,812, entitled “ROBOTIC SYSTEM INCLUDING AN ELECTRICAL CLAMPING SYSTEM,” by Kenneth MIKALSEN et al., filed Mar. 19, 2020 and to U.S. patent application Ser. No. 63/031,945, entitled “LINEAR ACTUATOR WITH EX-ZONE 1 RATED HOUSING,” by Svein SØYLAND, filed May 29, 2020, of which both application are assigned to the current assignee hereof and incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates, in general, to the field of drilling and processing of wells. In particular, present embodiments relate to a system and method for manipulating tubulars during subterranean operations, and more particularly present embodiments relate to an electrically operated linear actuator for use on a rig floor.

BACKGROUND

Robots continue to advance the art of drilling and producing wells in the oil and gas industry. Robots can be powered by various means (e.g., hydraulic, pneumatic, electric, etc.). Hydraulics or pneumatics reduce the risk of developing sparks on a rig floor, where volatile fluids and gases may be present. However, using electric power can significantly increase the risk of sparks occurring during robot operation in areas that are susceptible to having volatile fluids and gases present (e.g., a rig floor), while possibly reducing necessary support equipment, such as fluid pumps, for rig operations.

Standards have been developed to guide the design of equipment to be used in these hazardous areas. Two standards (ATEX and IECEx) are generally synonymous with each other and provide guidelines (or directives) for equipment design. Each standard identifies groupings of multiple explosive (EX) zones to indicate various levels of hazardous conditions in a target area. ATEX is an abbreviation for “Atmosphere Explosible”. IECEx stands for the certification by the International Electrotechnical Commission for Explosive Atmospheres.

One grouping is for areas with hazardous gas, vapor, and/or mist concentrations.

EX Zone 0—A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor or mist is present continuously or for long periods or frequently

EX Zone 1—A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor or mist is likely to occur in normal operation occasionally.

EX Zone 2—A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

Another grouping is for areas with hazardous powder and/or dust concentrations.

EX Zone 20—A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, or for long periods or frequently.

EX Zone 21—A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally.

EX Zone 22—A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

The Zone normally associated with the oil and gas industry is the EX Zone 1. Therefore, the explosive atmosphere directives or guidelines for robotic systems used in subterranean operations are for an EX Zone 1 environment. Explosive atmosphere directives or guidelines for other EX Zones can be used also (e.g., EX Zone 21). However, the EX Zone 1 and possibly EX Zone 21 seem to be the most applicable for the oil and gas industry. ATEX is the name commonly given to two European Directives for controlling explosive atmospheres: 1) Directive 99/92/EC (also known as ‘ATEX 137’ or the ‘ATEX Workplace Directive’) on minimum requirements for improving the health and safety protection of workers potentially at risk from explosive atmospheres. 2) Directive 94/9/EC (also known as ‘ATEX 95’ or ‘the ATEX Equipment Directive’) on the approximation of the laws of Member States concerning equipment and protective systems intended for use in potentially explosive atmospheres. Therefore, as used herein “ATEX certified” indicates that the article (such as an elevator, pipe handling robot, iron roughneck, etc.) meets the requirements of the two stated directives ATEX 137 and ATEX 95 for EX Zone 1 environments.

IECEx is a voluntary system which provides an internationally accepted means of proving compliance with IEC standards. IEC standards are used in many national approval schemes and as such, IECEx certification can be used to support national compliance, negating the need in most cases for additional testing. Therefore, as used herein, “IECEx certified” indicates that the article (such as an elevator or pipe handling robotic system) meets the requirements defined in the IEC standards for EX Zone 1 environments. As used herein, “EX Zone 1 certified (or certification)” or “EX certification” refers to ATEX certification, IECEx certification, or both for EX Zone 1 environments. As used herein, “EX certifiable” refers to a volume or housing that is configured and designed to meet the requirements of the EX Zone 1 for either the ATEX certification, or the IECEx certification, or both.

Rig floor equipment, such as pipe handlers and iron roughnecks, can been operated via hydraulic power. For example, iron roughnecks can have grippers that are extended into engagement with a joint in a tubular string to make or break the joint while tripping “in” or “out” the tubular string in a wellbore. The force requirements for making or breaking a joint in a segmented tubular string can be on the order of 250 kNm, while the space requirements to engage tubular ends that make up the joint can be rather small when compared to the amount of force to be applied in the limited space.

FIG. 7A illustrates examples of the varied space constraints for an iron roughneck to accommodate tubular strings 66 of various diameters. As described in more detail below, tubulars 60 that can be used to make up tubular strings 66 can have hard-banding 57 on the box end, which should not be engaged with die (or grippers) of either a torque wrench or a backup tong of an iron roughneck. Additionally, due to a reduced wall thickness at the end of a box end of the tubular 60, it is recommended that the die not engage the box end within 2 inches from the end of the box end. This further restricts the engagement area available to grip the box end during make or break operations. With the reduced engagement area and resulting reduced die heights of the torque wrench or backup tong, increased force density for each die is required to provide up to 250 kNm rotational force to the tubular string joint. The support equipment and structures in the iron roughneck needed to supply the 250 kNm torsional force to the joint must be robust enough to withstand the strains and stresses of applying this amount of force to the joint.

Using hydraulically powered equipment has been able to supply the needed force for the pipe handling equipment in use today. However, the support equipment needed for supplying the pressurized hydraulic fluid to the rig equipment is bulky, hazardous, messy, and the hydraulic pressures used to drive the rig equipment can be dangerous.

Electric motors have been used to replace hydraulic power in some equipment. However, use of electric motors in some areas has still not been accepted because of the overall system requirements, including conforming to the EX certification requirements. The iron roughneck is a good example of this, by requiring that a very high engagement force be applied to a substantially small area, with the iron roughneck supporting a wide range of tubular string diameters. The inventors of the current disclosure discovered, through their initial product designs, that a novel configuration of components was needed to accommodate the force, space, and EX certification requirements. The initial designs supported the force and EX certification requirements, but the bulk needed to apply the force in these designs prevented the size reduction needed to accommodate the wide range of tubular string diameters.

Therefore, improvements in the art of robotic systems for the oil and gas industry are continually needed.

SUMMARY

In accordance with an aspect of the disclosure, a tool for conducting a subterranean operation is provided. The tool can include a linear actuator assembly that can include an electric motor contained in an EX certifiable housing, a linear actuator external to the EX certifiable housing, the linear actuator coupled to and driven by the electric motor, the linear actuator having a first axis and a body, and a piston of the linear actuator that extends or retracts relative to the body when the linear actuator is driven by the electric motor, the piston having a second axis, with the first axis and the second axis being parallel and spaced apart.

In accordance with another aspect of the disclosure, a system for conducting a subterranean operation is provided. The system can include an iron roughneck with a torque wrench having a plurality of actuator assemblies circumferentially positioned around an opening through the iron roughneck, where the opening is configured to receive a tubular string, and where each of the actuator assemblies can include an electric motor contained in an EX certifiable housing, a linear actuator with a piston that extends or contracts in response to rotation of a coupling between the electric motor and the linear actuator, and a structure attached to an end of the piston, the structure being configured to engage the tubular string with a gripper when the piston is extended toward the tubular string and transfer a torsional force away from the piston when the gripper is engaged with the tubular.

In accordance with another aspect of the disclosure, a system for conducting a subterranean operation is provided. The system can include an iron roughneck with a torque wrench and a backup tong, each having multiple actuator assemblies which are circumferentially positioned around an opening through the iron roughneck, the opening being configured to receive a tubular string, wherein each of the actuator assemblies comprise an electric motor contained in an EX certifiable housing, and wherein a the iron roughneck is configured to provide a minimum vertical spacing of 2 inches (50.8 mm) between a top of a backup tong gripper and a bottom of a torque wrench gripper, and the iron roughneck is configured to deliver up to 250 kNm of torsional force to the tubular string at a minimum vertical spacing.

In accordance with another aspect of the disclosure, a method for making or breaking a joint in a tubular string is provided. The method can include operations of positioning the joint within a vertical opening that extends through an iron roughneck, with the iron roughneck comprising a torque wrench and a backup tong, engaging the joint with the backup tong and the torque wrench, wherein an overall height of an engagement of the joint is less than 400 mm, and wherein the overall height is defined as a distance along the joint from a top of an engagement of the torque wrench to a bottom of an engagement of the backup tong, and making or breaking the joint by rotating the torque wrench relative to the backup tong.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of present embodiments will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a representative view of a rig that can be used to perform subterranean operations, in accordance with certain embodiments;

FIG. 2 is representative perspective view of robots that can be used on a drill floor of a rig during subterranean operations, in accordance with certain embodiments;

FIGS. 3A and 3B are representative perspective views of a robotic iron roughneck, in accordance with certain embodiments;

FIG. 4 is a representative partial cross-sectional view of a tubular, in accordance with certain embodiments;

FIG. 5 is a representative partial cross-sectional view of a joint connection of a tubular string, in accordance with certain embodiments;

FIG. 6 is a representative perspective view of spacing for adjacent grippers in a robotic iron roughneck, in accordance with certain embodiments;

FIGS. 7A, 7B are representative side views of various tubular strings made up of various tubular sizes, with representative grippers (e.g., of an iron roughneck) positioned at a tubular joint connection in the tubular string, in accordance with certain embodiments;

FIG. 8 is a representative perspective view of a robotic iron roughneck with minimal space between torque wrench and backup tong, in accordance with certain embodiments;

FIG. 9 is a representative bottom view of a torque wrench of a robotic iron roughneck, in accordance with certain embodiments;

FIG. 10 is a representative perspective view of a backup tong of a robotic iron roughneck, in accordance with certain embodiments;

FIGS. 11-14 are representative perspective views of a linear actuator assembly that can be used in an example torque wrench or an example backup tong, in accordance with certain embodiments;

FIGS. 15-16 are representative perspective partially transparent views of a portion of a linear actuator assembly, in accordance with certain embodiments;

FIGS. 17-18 are representative partial cross-sectional views of a motor drive for a linear actuator assembly, in accordance with certain embodiments; and

FIG. 19 is a representative partial cross-sectional view of a motor drive for a linear actuator assembly, in accordance with certain embodiments.

DETAILED DESCRIPTION

The following description in combination with the figures is provided to assist in understanding the teachings disclosed herein. The following discussion will focus on specific implementations and embodiments of the teachings. This focus is provided to assist in describing the teachings and should not be interpreted as a limitation on the scope or applicability of the teachings.

As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

The use of “a” or “an” is employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural, or vice versa, unless it is clear that it is meant otherwise.

The use of the word “about”, “approximately”, or “substantially” is intended to mean that a value of a parameter is close to a stated value or position. However, minor differences may prevent the values or positions from being exactly as stated. Thus, differences of up to ten percent (10%) for the value are reasonable differences from the ideal goal of exactly as described. A significant difference can be when the difference is greater than ten percent (10%).

FIG. 1 is a representative view of a rig 10 that can be used to perform subterranean operations. The rig 10 is shown as an offshore rig, but it should be understood that the principles of this disclosure are equally applicable to onshore rigs as well. The example rig 10 can include a platform 12 with a derrick 14 extending above the platform 12 from the rig floor 16. The platform 12 and derrick 14 provide the general super structure of the rig 10 from which the rig equipment is supported. The rig 10 can include a horizontal storage area 18, pipe handlers 30, 32, 34, a drill floor robot 20, an iron roughneck 40, a crane 19, and fingerboards 80. The equipment on the rig 10, can be communicatively coupled to a rig controller 50 via a network 54, with the network 54 being wired or wirelessly connected to the equipment.

Some of the equipment that can be used during subterranean operations is shown in the horizontal storage area 18 and the fingerboards 80, such as the tubulars 60, the tools 62, and the bottom hole assembly (BHA) 64. The tubulars 60 can include drilling tubular segments, casing tubular segments, and tubular stands that are made up of multiple tubular segments. The tools 62 can include centralizers, subs, slips, adapters, etc. The BHA 64 can include drill collars, instrumentation, and a drill bit.

FIG. 2 is representative perspective view of some robots that can be used on a drill floor 16 of a rig 10 during subterranean operations. FIG. 2 shows a drill floor robot 20 gripping a tool 62 at the top end of the tubular string 66. The gripper 22 can engage the tool 62 and spin it off the top of the tubular string 66 in preparation for installing a tubular 60 to the end of the tubular string 66. The pipe handler 32 can engage a tubular 60 with the grippers 36 and move the tubular 60 from a storage location or the pipe handler 30 to a well center 82 where the pipe handler 32 can thread the tubular 60 onto the tubular string 66. The iron roughneck 40 can then torque the joint via torque wrench 42 and backup tong 44. When tripping the tubular string 66 from the wellbore, the iron roughneck 40 can be used to break lose the joint via the wrenches 42, 44.

FIG. 3A is a representative perspective view of a robotic iron roughneck 40, in accordance with certain embodiments. The iron roughneck 40 can include a chassis 48 with left and right channels 46 a, 46 b, respectively, to which the torque wrench 42 and the backup tong 44 can be slidingly coupled for up and down movement along the channels 46 a, 46 b. The torque wrench 42 and backup tong 44 can be arranged in parallel planes that are spaced apart and are generally perpendicular to the channels 46 a, 46 b. As the torque wrench 42 and backup tong 44 are moved up or down in the channels 46 a, 46 b, the gap L1 between them can vary. The minimum gap L1 that is achievable by this or other iron roughnecks 40 can determine the minimum achievable spacing between grippers (e.g., die) in the torque wrench 42 and grippers (e.g., die) in the backup tong 44. This minimum achievable spacing can determine the minimum size tubular joints in a tubular string 66 the iron roughneck 40 can make or break, since smaller tubulars 60 can require smaller and smaller spacing between the grippers in the torque wrench 42 and the grippers in the backup tong 44. The gap L1 for the current disclosure can be less than 100 mm, or 80 mm, or 75 mm, or 70 mm, or 65 mm, or 60 mm.

The backup tong 44 can include multiple grippers (or die) configured to engage a tubular string 66. The backup tong 44 includes a configuration of novel linear actuator assemblies that can drive the grippers into engagement with the tubular string 66 and can hold one end (e.g., a box end) of a joint in a tubular string 66 from rotating while the torque wrench delivers up to 250 kNm torsional force to the mating end (e.g., a pin end) of the joint in the tubular string 66, when the grippers are engaged with the one end (e.g., a box end) of the joint in the tubular string 66.

The torque wrench 42 can include a drive motor assembly 42 b and a gripper assembly 42 a that can include a similar configuration of linear actuator assemblies that can drive the grippers into engagement with the tubular string 66 and deliver up to 250 kNm torsional force to an end (e.g., a pin end) of a joint in the tubular string 66, when the grippers are engaged with the tubular string 66. The torque wrench 42 and the backup tong 44 are configured to move vertically up or down as needed to align with the respective tubular ends of the joint in the tubular string 66. Generally, the grippers of the backup tong 44 are aligned with the box end of the joint in the tubular string 66 and the grippers of the torque wrench 42 are aligned with the pin end of the joint in the tubular string 66, when the roughneck is being used to make or break a joint in the tubular string 66. The overall height L21 of the combination of the torque wrench 42 and the backup tong 44 can vary as the torque wrench 42 and the backup tong 44 are moved up or down during operation of the roughneck 40. The overall height L21 can include the drive motor assembly 42 b, the gripper assembly 42 a, the gap L1 between the torque wrench 42 and the backup tong 44, and the backup tong 44. The height L20 can include the gripper assembly 42 a, the gap L1, and the backup tong 44.

In some embodiments, such as the iron roughneck 40 shown in FIG. 3B, the drive motor assembly 42 b and the gripper assembly 42 a can be enclosed in a common chassis. However, the overall height L20 would still indicate the overall height of the gripper assembly 42 a, the gap L1, and the backup tong 44, with L21 still including the drive motor assembly 42 b, the gripper assembly 42 a, the gap L1 between the torque wrench 42 and the backup tong 44, and the backup tong 44.

When the torque wrench 42 is positioned at a minimum distance from the backup tong 44, then the heights L20 and L21 can be at their minimum distance. The configuration of the novel linear actuator assemblies in the torque wrench 42 and the backup tong 44 allows for the gap L1 to be at a minimum vertical distance of less than 100 mm, or 80 mm, or 75 mm, or 70 mm, or 65 mm, or 60 mm. Additionally, the configuration of the novel linear actuator assemblies in the torque wrench 42 and the backup tong 44 allows for the overall vertical distance L20 to be at a minimum vertical distance of less than 500 mm, or 450 mm, or 440 mm, or 430 mm, or 420 mm, or 410 mm. Additionally, the configuration of the novel linear actuator assemblies in the torque wrench 42 and the backup tong 44 allows for the overall vertical distance L21 to be at a minimum vertical distance of less than 800 mm, or 790 mm, or 750 mm, or 740 mm, or 730 mm, or 720 mm , or 710 mm. These minimum vertical distances allow the iron roughneck of the current disclosure to support a wide range of tubular diameters (e.g., 3.5 inches to 14.0 inches) and a wide range of torsional torqueing forces (e.g., up to 250 kNm torsional force).

FIG. 4 is a representative partial cross-sectional view of a tubular 60. Each tubular 60 can include a box end 67 and a pin end 69. The box end 67 can include a weldment 74 to the body 61 of the tubular 60, a tool joint box 57, a hard-banding area 70, an elevator shoulder 72, end shoulder 86, and internal box threads 90. The body 61 can include an internal upset 76 and an external upset 78 proximate the weldments 74, and an internal coating 80. The pin end 69 can include a weldment 74 to the body 61 of the tubular 60, a tool joint pin 56, pin taper 73, a primary shoulder 82, a secondary shoulder 84, and external pin threads 92. When a pin end 69 is connected to a box end 67, the external threads 92 of the pin end 69 are inserted in the box end 67 and engaged with the internal threads 90 of the box end 67. The connection can be rotated to further thread the pin end 69 into the box end 67 until the primary shoulder 82 engages the end shoulder 86. The secondary shoulder 84 can also engage a bottom of the thread portion of the box end 67. At this point, an iron roughneck 40 can be used to torque the pin end 69 relative to the box end 67 to a specified torque amount. To unthread the pin end 69 from the box end 67, the iron roughneck 40 can apply an un-torqueing force to the pin end 69 relative to the box end 67, to break the tubular joint connection and allow the pin end 69 to be unthreaded from the box end 67.

FIG. 5 is a representative partial cross-sectional view of a joint connection 68 between a pin end 69 and a box end 67 in a tubular string 66, in accordance with certain embodiments. The internal flow passage of the tubular string 66 can be diameter D2. The diameter D1 is the outer diameter of the tubular joint 68. The diameter D3 is the outer diameter of the tubular body 61. When the pin end 69 is threaded into the box end 67, the primary shoulder 84 of pin end 69 can abut the end shoulder 86 of the box end 67. The interface 88 indicates the abutment of the primary shoulder 84 and the end shoulder 86. The tubular joint 68 can include three major regions. The tool joint pin region 56 indicates the region available to the torque wrench 42 for gripping the pin end 69 with a plurality of grippers 200 (see FIG. 6). The longitudinal distance L2 indicates the length of the tool joint pin region 56.

The tool joint box region 57 indicates the region available to the backup tong 44 for gripping the box end 67 with a plurality of grippers 202 (see FIG. 6). The longitudinal distance L3 indicates the length of the tool joint box region 57. However, the grippers 202 of the backup tong 44 should not engage the region 57 within a minimum distance L4 from the end shoulder 86. This is generally due to a reduced thickness of the wall of the box end 67 proximate the end shoulder 86. It is recommended that L4 be a minimum of 2 inches (50.8 mm) from the end shoulder 86. Therefore, the remaining portion of the region 57 that is available to engage the plurality of grippers 202 of the backup tong 44 is a distance L3 minus distance L4, which equals a longitudinal distance L5 (i.e., L3−L4=L5).

The hard-banding region 58 indicates the region of the box end 67 that the plurality of grippers 202 of the backup tong 44 should not engage. The longitudinal distance L6 indicates the length of the hard-banding region 56.

According to the “API SPEC 5DP 1st Edition, August 2009”:

the shortest tool joint pin region 56 (i.e., L2) is 7 inches (177.8 mm),

the shortest tool joint box region 57 and 58 (i.e., L3+L6) is 8 inches (203.2 mm),

the longest tool joint pin region 56 (i.e., L2) is 8 inches (203.2 mm), and

the longest tool joint box region 57 and 58 (i.e., L3+L6) is 11 inches (279.4 mm).

Therefore, the minimum length L2 for the tool joint pin region 56 can be 7 inches (177.8 mm), and the minimum length L3+L6 for the tool joint box region 57 can be 8 inches (203.2 mm). L3+L6 (e.g., 8 inches) minus (L6+L4) can determine the minimum length L5 available for the grippers of the backup tong to engage the box end 67. The length L5 indicates the available region to engage the plurality of grippers 202 in the box region 57. Length L5 can be a minimum of 3.9375 inches (99.61 mm), or a minimum of 3 inches (76.2 mm), or a minimum of 2 inches (50.8 mm).

FIG. 6 is a representative perspective view of spacing for adjacent grippers 200, 202 in a robotic iron roughneck 40, in accordance with certain embodiments. This spacing is in a longitudinal direction that is parallel to the longitudinal direction of the tubular string 66. Therefore, if the tubular string 66 is generally vertical relative to the rig floor 16, then the spacing can be seen as vertical spacing. FIG. 6 is showing a gripper 200 in the torque wrench 42 above a gripper 202 in the backup tong 44, with a majority of other structures of the torque wrench 42 and backup tong 44 omitted for clarity. The gripper 200 of the torque wrench 42 can be a height L7 and gripper 202 of the backup tong 44 can be a height L9, where L7 and L9 can be different or equal heights. The vertical distance L8, measured from the top of the gripper 202 of the backup tong 44 to the bottom of the gripper 200 of the torque wrench 42, can be equal to the distance L4 (2 inches minimum).

However, due to the clamping forces (i.e., up to 700 kN per linear actuator assembly 100) needed from the plurality of grippers 200 or 202, gripping a variety of tubular diameters within the restricted vertical spacing available to engage the tubular joints (especially for the smaller tubulars 60), a novel solution, including novel linear actuator assemblies, was needed according to the inventors. The novel solution can enable a system, such as an iron roughneck, to apply the high engagement forces to the tubular joint, while supporting the minimum distances for engagement areas of the joint.

FIGS. 7A, 7B are representative side views of various tubular strings 66 a-h with various tubular sizes and representative grippers 200, 202 (e.g., of an iron roughneck) positioned at a tubular joint 68 in the tubular string 66 a-h. The center of the tubular joint 68 for each tubular string 66 a-h is indicated by the line 88. If a spinner assembly or pipe handler is being used to spin in or out tubulars 60 in the tubular string 66, then either of these are recommended to be positioned at least 475 mm (18.7 inches) above the line 88, assuming the grippers 200 of the torque wrench 42 are positioned just above the center of the joint 68 (line 88). Each joint 68 can include the tool joint pin region 56 with length L2, the tool joint box region 57 with length L3, and the hard-banding region 58 with length L6.

The respective heights L7 and L9 of the grippers 200, 202 can be 148 mm (5.83 inches), with the vertical distance L8 being 60 mm (2.36 inches). The tubular string 66 a can include tubulars 60 with a diameter D1 of 4 inches (101.6 mm) (refer to FIG. 5).

The tubular string 66 a can include a tubular joint 68 between a pin end 69 and a box end 67 having their maximum lengths for this diameter D1. For this example, the tool joint pin and box regions 56, 57 are also at their maximum lengths for this diameter D1 and are large enough to accommodate the grippers 200, 202 of height L7, L9, respectively, with the recommended minimum clearance L4 (2 inches) from the center line 88 in the tool joint box region 57. The gripper 200 can be positioned proximate the center line 88 (e.g., at or just above the center line 88), with the gripper 200 positioned above the gripper 202 by the gap distance L8 and having sufficient spacing between the gripper 202 and the hard-banding region 58.

The tubular string 66 b can include tubulars 60 with a diameter D1 of 4 inches (101.6 mm). The tubular string 66 b can include a tubular joint 68 between a pin end 69 and a box end 67 each having their minimum lengths for this diameter D1. The tool joint pin and box regions 56, 57 are also at their minimum lengths for this diameter D1, yet they are still large enough to accommodate the grippers 200, 202 of height L7, L9, respectively, with the recommended minimum clearance L4 (2 inches) from the center line 88 in the tool joint box region 57. However, the gripper 200 is about the same height or a bit larger than the tool joint pin region 56 in this example. The gripper 200 can be positioned proximate the center line 88 (e.g., at or just above the center line 88), with the gripper 200 positioned above the gripper 202 by the gap distance L8 and having sufficient spacing between the gripper 202 and the hard-banding region 58.

The tubular string 66 c can include tubulars 60 with a diameter D1 of 5.875 inches (149 mm). The tubular string 66 c can include a tubular joint 68 between a pin end 69 and a box end 67 each having their maximum lengths for this diameter D1. The tool joint pin and box regions 56, 57 are also at their maximum lengths for this diameter D1 and are large enough to accommodate the grippers 200, 202 of height L7, L9, respectively, with the recommended minimum clearance L4 (2 inches) from the center line 88 in the tool joint box region 57. The gripper 200 can be positioned proximate the center line 88 (e.g., at or just above the center line 88), with the gripper 200 positioned above the gripper 202 by the gap distance L8 and having sufficient spacing between the gripper 202 and the hard-banding region 58.

The tubular string 66 d can include tubulars 60 with a diameter D1 of 5.875 inches (149 mm). The tubular string 66 a can include a tubular joint 68 between a pin end 69 and a box end 67 each having their minimum lengths for this diameter D1. The tool joint pin and box regions 56, 57 are also at their minimum lengths for this diameter D1, yet they are still large enough to accommodate the grippers 200, 202 of height L7, L9, respectively, with the recommended minimum clearance L4 (2 inches) from the center line 88 in the tool joint box region 57. However, the gripper 200 is about the same height or a bit larger than the tool joint pin region 56 in this example. The gripper 200 can be positioned proximate (e.g., at or just above the center line 88), with the gripper 200 positioned above the gripper 202 by the gap distance L8 and having sufficient spacing between the gripper 202 and the hard-banding region 58.

The tubular string 66 e can include tubulars 60 with a diameter D1 of 6.625 inches (168 mm). The tubular string 66 e can include a tubular joint 68 between a pin end 69 and a box end 67 each having their maximum lengths for this diameter D1. The tool joint pin and box regions 56, 57 are also at their maximum lengths for this diameter D1 and are still large enough to accommodate the grippers 200, 202 of height L7, L9, respectively, with the recommended minimum clearance L4 (2 inches) from the center line 88 in the tool joint box region 57. The gripper 200 can be positioned proximate the center line 88 (e.g., at or just above the center line 88), with the gripper 200 positioned above the gripper 202 by the gap distance L8 and having sufficient spacing between the gripper 202 and the hard-banding region 58.

The tubular string 66 f can include tubulars 60 with a diameter D1 of 6.625 inches (168 mm). The tubular string 66 f can include a tubular joint 68 between a pin end 69 and a box end 67 each having their minimum lengths for this diameter D1. The tool joint pin and box regions 56, 57 are also at their minimum lengths for this diameter D1. The tool joint box region 57 is not large enough to accommodate the grippers 202 of height L9 and the recommended minimum clearance L4 (2 inches) from the center line 88. Therefore, the gripper 202 has been moved up to prevent engagement of the gripper 202 with the hard-banding region 58. The tool joint pin region 56 could have possibly accommodated the gripper 200 of height L7, but since the gripper 202 is moved up, it cannot allow the recommended minimum clearance L4 (2 inches) from the center line 88 and the gripper 200 must also move up because of the gap distance L8 between the grippers 200, 202 due to the structures required to hold and operate the torque wrench 42 and backup tong 44. If the gap length L8 were smaller (e.g., heights of the structures being less), then this could reduce the impact on spacing of the grippers and engaging the tubular joint 68.

The tubular string 66 g can include tubulars 60 with a diameter D1 of 2.875 inches (73 mm). The tubular string 66 g can include a tubular joint 68 between a pin end 69 and a box end 67 each having their maximum lengths for this diameter D1. The tool joint pin and box regions 56, 57 are also at their maximum lengths for this diameter D1. In this case, even for the maximum lengths, the tool joint box region 57 is not large enough to accommodate the grippers 202 of height L9 and the recommended minimum clearance L4 (2 inches) from the center line 88. Therefore, the gripper 202 has been moved up to prevent engagement of the gripper 202 and the hard-banding region 58. The tool joint pin region 56 could have possibly accommodated the gripper 200 of height L7, but since the gripper 202 has been moved up, it cannot allow the recommended minimum clearance L4 (2 inches) from the center line 88 and the gripper 200 must also be moved up because of the gap distance L8 between the grippers 200, 202 due to the structures required to hold and operate the torque wrench 42 and backup tong 44. If the gap length L8 were smaller (e.g., heights of the structures being less), then this could reduce the impact on spacing of the grippers and engaging the tubular joint 68.

The tubular string 66 h can include tubulars 60 with a diameter D1 of 2.875 inches (73 mm). The tubular string 66 h can include a tubular joint 68 between a pin end 69 and a box end 67 each having their minimum lengths for this diameter D1. The tool joint pin and box regions 56, 57 are also at their minimum lengths for this diameter D1. In this case, neither the tool joint pin region 56 nor the tool joint box region 57 are large enough to accommodate the grippers 200 or 202. Even with the gripper 202 justified up to the center line 88 (i.e., length L4 approximately equal to “0”) it can still overlap the hard-banding region 58. The gripper 200 is spaced away from the gripper 202 by the gap L8, which can cause the gripper 200 to extend past the tool joint pin region 56, with less than half of the gripper 200 engaging the tubular joint 68.

FIG. 7B shows the tubular joint 68 of the tubular string 66 h in greater detail. The length L2 is less than the length L7 plus the length L8. The gripper 200 is spaced away from the center line 88 by the gap L8, since the gripper 202 is adjusted up to the center line 88. The length L3 is less than the length L9. The engagement of the gripper 202 does not allow for the minimum clearance L4 from the center line 88 and it overlaps the hard-banding region 58. This configuration can be improved by minimizing the gap length L8, as described in this disclosure.

Another possible approach to engage the gripper 200 with only the tool joint pin end 56 and engage the gripper 202 with only the tool joint box end 57 (minus the length L4 space) in cases with a smaller tubular strings (e.g., a diameter D1 of 2.875 inches (73 mm)) the grippers 200, 202 can be replaced with modified grippers 200′, 202′ as shown in FIG. 7B. The modified gripper 200′ can include a reduced engagement area positioned toward the bottom of the gripper 200′, with the upper portion of the gripper 200′ tapered away from the tubular joint 68. The modified gripper 202′ can include a reduced engagement area positioned toward the top of the gripper 200′, with the lower portion of the gripper 202′ tapered away from the tubular joint 68.

The modified grippers 200′, 202′ can have the same heights L7, L9, respectively, of the grippers 200, 202, so they can be attached to the torque wrench 42 and backup tong 44, respectively, with the same attachment mechanism used to attach the grippers 200, 202. With the reduced engagement area of the grippers 200′, 202′, the engagement area of the gripper 202′ can again be positioned a distance L4 (minimum 2 inches) from the center line 88, and the engagement area of the gripper 200′ can be positioned completely within the tool joint pin region 56. Therefore, it is beneficial to reduce the gap length L8 to as small as possible to enable the grippers 200, 202, 200′, and 202′ to engage the desired regions on the joint 68.

FIG. 8 is a representative perspective view of a robotic iron roughneck 40 with vertical distance L1 between the torque wrench 42 and the backup tong 44. This iron roughneck 40 configuration minimizes the gap length L8 (and thus the vertical distance L1) between the grippers 200, 202 by minimizing heights of structures used to support and operate the grippers 200, 202.

FIG. 9 is a representative bottom view of a torque wrench 42 of a robotic iron roughneck 40. The torque wrench 42 can include a rotational assembly 203 that can be rotated relative to the stationary assembly 204. Drive gears 240, 242 can operate drive chains 216, 218, respectively, to rotate the assembly 203 relative to the stationary assembly 204. The drive chains 216, 218 can engage opposite sides of the torque gear 214 to rotate the body 206 (arrows 290) of the rotational assembly 203. Multiple linear actuator assemblies 100 can be attached to the rotational body 206 and arranged around a central axis 220 of an opening 208 in the torque wrench 42. Each linear actuator assembly 100 can include a gripper 200, 200′ that is positioned around the central axis 220. The body 206 can include supports 210, 212 that provide structural support for the linear actuators 100 and the rotational body 206. The linear actuator assemblies 100 can be designed to be EX Zone 1 certifiable with each including a purged chamber that is kept at an elevated pressure above an environmental pressure external to the assemblies 100 and that is periodically (or continually) flushed with a gas (e.g., air) to comply with EX Zone 1 requirements for equipment to be used in hazardous areas, such as rig floors, where sparks could cause significant damage by igniting volatile gases or liquids. The purged chambers in the torque wrench 42 can be supplied with pressurized gas through air channels 270, 272, 274, 276, 278.

FIG. 10 is a representative perspective view of a backup tong 44 for a robotic iron roughneck 40. The backup tong 44 can include a body 226 that supports multiple linear actuator assemblies 100 attached to the body 226 and arranged around a central axis 220 of an opening 228 in the backup tong 44 (with the center axis 220 being common the opening 228 of the torque wrench 42). Each linear actuator assembly 100 can include a gripper 202, 202′ that is positioned around the central axis 220. The body 226 can include supports 230, 232 that provide structural support for the linear actuator assemblies 100 and the body 226. The linear actuator assemblies 100 can be designed to be EX Zone 1 certifiable with each including a purged chamber that is kept at an elevated pressure above an environmental pressure external to the assemblies 100 and that is periodically (or continually) flushed with a gas (e.g., air) to comply with EX Zone 1 requirements for equipment to be used in hazardous areas, such as rig floors, where sparks could cause significant damage by igniting volatile gases or liquids. The purged chambers in the backup tong 44 can be supplied with pressurized gas through air channels 280, 282, 284, 286, 288.

FIG. 11 is a representative perspective view of a linear actuator assembly 100 for an example torque wrench 42 or an example backup tong 44, in accordance with certain embodiments. It should be understood that the linear actuator assembly 100 in all of the example embodiments can also be used in applications other than an iron roughneck, where a very large extension force is required from a compact volume.

The linear actuator assembly 100 can include a motor assembly 110 that houses an electric drive motor. The drive motor can be drivingly coupled to a linear actuator 150 via a gear box 120, which can be completely or at least partially filled with fluid (e.g., oil). The linear actuator 150 can extend or retract a piston 170 (arrows 292). A structure 180 can be attached to an end of the piston 170 and can be retracted and extended with the piston 170. The structure 180 can include a head portion 181 configured to removably attach a gripper 200 or 202 (or a gripper 200′ or 202′). The structure 180 can also include a guide portion 184 that is attached to the head portion 181 via a reduced thickness portion 182. The reduced thickness portion 182 and the guide portion 184 can form a horizontal “T-shaped” structure attached to the head portion 181 and extending to one side of the head portion 181.

The guide portion 184 can engage grooves in supports 210, 212, 230, 232, where the grooves allow the structure 180 to extend and retract with the piston 170, while preventing torsional forces (arrows 294) from being applied to the piston 170. Therefore, the piston 170 can be designed to withstand the compression forces applied to it by the linear actuator 150 when the piston 170 is extended such that the gripper 200 or 202 attached to the structure 180 engages a tubular joint 68. However, the piston 170 does not need to withstand torsional forces (arrows 294) when the tubular joint 68 is engaged and being torqued by the iron roughneck 40, because the structure 180 can redirect these torsional forces away from the piston 170 and to the body of the torque wrench 42 or the backup tong 44.

The motor assembly 110 can have a length L10, a width L11, and a height L12. The height L12 can be the same length as the height L7 of the gripper 200, 202. The length L13 can include the motor assembly 110 and the linear actuator 150. The width L14 can include the gear box 120 and the stationary portion of the linear actuator 150. The height L15 can indicate the height of the stationary portion of the linear actuator 150. The height L15 can be the same height as the height L7 of the grippers 200, 202. The length L18 can indicate the distance from an end of the stationary portion of the linear actuator 150 to the end of the gripper 200, 202. The length L19 can indicate the stroke length of the piston 170, where the length L19 can be from “0” to 170 mm. The length L17 can indicate the size of the interface body 190. Electrical input/output connections 192, 194 can interface the linear actuator assembly 100 to the power and control from the robotic iron roughneck 40 (or any other system in which the linear actuator assembly 100 is used).

The length L10 can be up to 235 mm. The width L11 can be up to 260 mm. The height L12 can be up to 170 mm. Therefore, a first overall volume of the EX Certifiable housing 110 can be up to 10.4K cm³. The length L13 can be up to 460 mm. The width L14 can be 383 mm. The height L15 can be up to 180 mm. Therefore, a second overall volume can include the stationary portion of the linear actuator assembly 100 (i.e., EX certifiable housing 110, gear box 120, and body 154 of the linear actuator 150) and can be up to 31.7K cm³. The length L18 can range from 151 mm to 321 mm, with length L19 being representative of the stroke length of the piston 170, which can range from “0” to 170 mm. The length L17 can be up to 150 mm.

FIG. 12 is a representative perspective semi-transparent view of a linear actuator assembly 100, in accordance with certain embodiments. The discussion of the linear actuator assembly 100 in FIG. 11 applies to the like items in FIG. 12 equally as well. FIG. 12 further indicates an electric drive motor 112 contained within a purged chamber 114 of a housing 113. The purged chamber 114 extends into the interface body 190, which is connected to the housing 113, and receives pressurized gas (e.g., air) from the ports 266, 268. These ports 266, 268 can be connected to air channels (such as air channels 270, 272, 274, 276, 278, 280, 282, 284, 286, 288) that can supply the pressurized gas to the purged chamber 114.

FIG. 13 is a representative perspective view of a linear actuator assembly 100 for an example torque wrench 42, an example backup tong 44 of a robotic iron roughneck 40, or other rig equipment, in accordance with certain embodiments. FIG. 13 illustrates that the linear actuator assembly 100 can be configured for left or right configurations, with the left configuration shown in FIG. 13 and the right configuration shown in FIG. 12. The torque wrench 42 in FIG. 9 and the backup tong in FIG. 10 each show two left configured linear actuator assemblies 100 and one right configured linear actuator assembly 100.

FIG. 14 is a representative perspective view of a linear actuator assembly 100 for an example torque wrench 42 or an example backup tong 44 of a robotic iron roughneck 40, in accordance with certain embodiments. The discussion of the linear actuator assembly 100 in FIGS. 11-13 apply to the like items in FIG. 14 equally as well. FIG. 14 further shows more internal components of the linear actuator assembly 100 than in the previous figures. The motor 112 drives the gears in the gear box 120. The actuator drive gear 128 drives the threaded shaft 152 in the housing (or body) 154 of the linear actuator 150. Rotating the actuator drive gear 128 can rotate the threaded drive shaft 152 and thread it into and out of the piston 170, thereby extending or retracting the piston 170. The linear actuator 150 can also include a housing 154 that can constrain the piston 170 from rotating while the threaded drive shaft 152 rotates. The housing 154 can engage features on the threaded sleeve 172 to prevent the piston's rotation and constraining the piston 170 to extend or retract axially without rotating. An outer sleeve 174 can sealing engage the housing 154 to prevent fluids or debris from entering the linear actuator 150.

FIGS. 15-16 are representative perspective partially transparent views of a gear box 120 portion of a linear actuator assembly 100, in accordance with certain embodiments. It should be understood that the gear box can contain several different gear coupling mechanism 122 configurations which can each transfer a rotational force from a drive shaft of the motor 112 to rotation of a drive shaft in the linear actuator 150. FIGS. 15-16 show an exemplary gear coupling mechanism 122 configuration of gears in the gear box 120.

The electric drive motor 112 can have a drive shaft that extends from the purged chamber 114 into the gear box chamber 120 and rotates a drive gear 124. The drive gear 124 can be coupled to an intermediate drive gear 126 that can transfer a rotational force from the drive gear 124 to a drive gear 128. The drive gear 128 can be rotationally fixed to a drive shaft of the linear actuator 150, such that rotation of the drive gear 128 rotates the drive shaft to actuate the linear actuator 150. To meet APEX standards for EX zone 1 environments, the gear chamber 132 of the gear box 120 is at least partially filled with a fluid (e.g., oil) to lubricate the gears and prevent sparks from the gears during operation.

FIGS. 17-18 are representative partial cross-sectional views of a motor drive for a linear actuator assembly 100, in accordance with certain embodiments. The motor 112 can be rigidly attached to an inside of the housing 113 and positioned in the purged chamber 114. Seals 116, 117 can be used to sealingly engage the motor 112 to the housing 113, thereby preventing fluid in the gear box 120 from entering the purged chamber 114 and preventing gas in the purged chamber 114 from entering the gear box 120. The seal 118 can sealingly engage the cover 130 of the gear box 120 to the housing 113, thereby preventing fluid in the gear box 120 from exiting the gear box 120 into the external environment 264 and preventing fluid or debris in the external environment 264 from entering the gear box 120. The seal 134 can sealingly engage a lid 136 of the cover 130 to a body 138 of the cover 130, thereby preventing fluid in the gear box 120 from exiting the gear box 120 into the external environment 264 and preventing fluid or debris in the external environment 264 from entering the gear box 120.

The seal 140 can sealingly engage the interface body 190 to the housing 113, thereby preventing gas from exiting the in the purged chamber 114 into the external environment 264 between the housing 113 and the body 190, and preventing gas in the external environment 264 from entering the in the purged chamber 114 between the housing 113 and the body 190. The drive shaft 115 can be driven by the motor 112 to rotate the drive gear 124, which is rotationally fixed to the drive shaft 115.

FIG. 19 is a representative partial cross-sectional view of a motor drive for a linear actuator assembly 100, in accordance with certain embodiments. The gear coupling mechanism 122 couples the drive shaft 115 of the motor 112 to the drive shaft 152 of the linear actuator 150. The drive shaft 115 of the motor 115 can drive the gear 124, which can drive the intermediate gear 126. The intermediate gear 126 can then drive the gear 128, which can be rotationally fixed to a drive shaft 152 of the linear actuator 150. The drive shaft 152 can be threaded at one end that threadingly engages internal threads of a moveable sleeve 172. The sleeve 172 can be rotationally fixed to the housing 154 of the linear actuator 150, while being slidingly coupled to the housing 154. Therefore, as the threaded drive shaft 152 is rotated, the drive shaft 152 will rotate relative to the housing 154 and the sleeve 172, thereby threading the drive shaft 152 further into or out of the sleeve 172. Threading the drive shaft out of the sleeve 172 can cause the sleeve 172 to extend (arrows 292) from the housing 154. Threading the drive shaft into the sleeve 172 can cause the sleeve 172 to retract (arrows 292) into the housing 154. The head portion 181 of the structure 180 can include an internal bore 186 that is closed at the end 188. This can allow the drive shaft 152 to extend into the bore 186 as the piston 170 is retracted into the linear actuator 150.

The simplified configuration of the linear actuator assembly 100 provides significantly increased extension force (or gripping force) for the linear actuator 150 in a reduced volume allowing the linear actuator assembly 100 to support a pipe handler configuration (e.g., an iron roughneck) that can have a pair of wrench assemblies that can be spaced apart by a minimal vertical distance to accommodate breaking or making tubular joints 68.

VARIOUS EMBODIMENTS

Embodiment 1. A tool for conducting a subterranean operation, the tool comprising:

a linear actuator assembly that comprises:

an electric motor contained in an EX certifiable housing;

a linear actuator external to the EX certifiable housing, the linear actuator coupled to and driven by the electric motor, the linear actuator having a first axis and a body; and

a piston of the linear actuator that extends or retracts relative to the body when the linear actuator is driven by the electric motor, the piston having a second axis, with the first axis and the second axis being parallel and spaced apart.

Embodiment 2. The tool of embodiment 1, wherein the linear actuator is coupled to the electric motor via gears disposed in a fluid filled chamber.

Embodiment 3. The tool of embodiment 2, wherein seals disposed between the EX certifiable housing and the fluid filled chamber prevent pressurized gas from entering the fluid filled chamber and prevent fluid from the fluid filled chamber from entering the EX certifiable housing.

Embodiment 4. The tool of embodiment 3, wherein the fluid in the fluid filled chamber prevents sparks during operation of the gears.

Embodiment 5. The tool of embodiment 1, wherein an internal pressure of the EX certifiable housing is elevated above an environmental pressure external to the EX certifiable housing.

Embodiment 6. The tool of embodiment 1, wherein the EX certifiable housing receives pressurized gas through a gas inlet and exhausts the pressurized gas from the EX certifiable housing via a gas outlet, such that the pressurized gas in the EX certifiable housing is continually replaced with the pressurized gas received through the gas inlet.

Embodiment 7. The tool of embodiment 1, wherein the linear actuator further comprises a structure mounted to an end of the piston, wherein the structure is configured to:

engage a tubular,

transfer a longitudinal force of the piston to the tubular, and

direct a torsional force, applied to the tubular by the structure, away from the piston.

Embodiment 8. The tool of embodiment 7, wherein the structure comprises a gripper that is removably attached to the structure, the gripper being configured to engage the tubular when the piston extends toward the tubular.

Embodiment 9. The tool of embodiment 1, wherein the linear actuator assembly provides up to 700 kN clamping force when engaged with a tubular.

Embodiment 10. The tool of embodiment 9, wherein a first overall volume includes the EX certifiable housing, the body of the linear actuator, and a gear box for coupling the linear actuator to the electric motor, and wherein the first overall volume is less than 32K cubic cm.

Embodiment 11. The tool of embodiment 9, wherein the EX certifiable housing is contained in a second overall volume, and wherein the second overall volume is less than 11K cubic cm.

Embodiment 12. The tool of embodiment 9, wherein a vertical height of the EX certifiable housing is less than 200 mm.

Embodiment 13. The tool of embodiment 1, wherein the piston has a stroke length of up to 170 mm.

Embodiment 14. A system for conducting a subterranean operation, the system comprising:

an iron roughneck comprising a torque wrench having a plurality of actuator assemblies circumferentially positioned around an opening through the iron roughneck, wherein the opening is configured to receive a tubular string, and wherein each of the actuator assemblies comprise:

an electric motor contained in an EX certifiable housing;

a linear actuator with a piston that extends or contracts in response to rotation of a coupling between the electric motor and the linear actuator; and

a structure attached to an end of the piston, the structure being configured to engage the tubular string with a gripper when the piston is extended toward the tubular string and transfer a torsional force away from the piston when the gripper is engaged with the tubular.

Embodiment 15. The system of embodiment 14, wherein the torque wrench is configured to transfer up to 250 kNm of torsional force to the tubular string when the torque wrench is engaged with the tubular string.

Embodiment 16. The system of embodiment 14, wherein each of the actuator assemblies is rigidly attached to a body of the torque wrench, and wherein the torque wrench is configured to transfer a torsional force to the tubular string when the torque wrench is engaged with the tubular string.

Embodiment 17. The system of embodiment 16, wherein the structure transfers the torsional force to the body of the torque wrench and away from the piston.

Embodiment 18. The system of embodiment 16, wherein the structure comprises:

a head portion;

the gripper removably attached to the head portion; and

a T-shaped protrusion that extends from the head portion, wherein the T-shaped protrusion is slidingly engaged with a groove in the body of the torque wrench, and wherein the groove is complimentarily shaped to receive the T-shaped protrusion.

Embodiment 19. The system of embodiment 18, wherein the T-shaped protrusion engages the groove in the body of the torque wrench and transfers the torsional force through the T-shaped protrusion to the body and away from the piston.

Embodiment 20. The system of embodiment 14, wherein the iron roughneck further comprises a backup tong spaced vertically away from the torque wrench, the backup tong having another plurality of the actuator assemblies circumferentially positioned around the opening in the iron roughneck.

Embodiment 21. The system of embodiment 20, wherein the iron roughneck is configured to produce a minimum vertical distance from a top of one of the grippers in the backup tong to a bottom of one of the grippers in the torque wrench, and wherein the minimum vertical distance is 60 mm (2.36 inches).

Embodiment 22. The system of embodiment 21, wherein the minimum vertical distance is 65 mm (2.56 inches), or 70 mm (2.76 inches), or 75 mm (2.95 inches), or 80 mm (3.15 inches), or 85 mm (3.35 inches), or 90 mm (3.54 inches), or 95 mm (3.74 inches), or 100 mm (3.94 inches).

Embodiment 23. The system of embodiment 21, wherein a maximum height is less than 500 mm when the torque wrench is positioned adjacent the backup tong with the grippers in the backup tong being separated from the grippers in the torque wrench by the minimum vertical distance, with the maximum height including combined vertical heights of the backup tong, the torque wrench, and a vertical space between the backup tong and the torque wrench.

Embodiment 24. The system of embodiment 23, wherein the maximum height is less than 450 mm, or 440 mm, or 430 mm, or 420 mm, or 410 mm.

Embodiment 25. The system of embodiment 23, wherein the torque wrench and backup tong are configured to transfer up to 250 kNm of torsional force to the tubular string when the torque wrench and the backup tong are engaged with the tubular string.

Embodiment 26. A system for conducting a subterranean operation, the system comprising:

an iron roughneck with a torque wrench and a backup tong, each having multiple actuator assemblies which are circumferentially positioned around an opening through the iron roughneck, the opening being configured to receive a tubular string, wherein each of the actuator assemblies comprise an electric motor contained in an EX certifiable housing, and wherein a the iron roughneck is configured to provide a minimum vertical spacing of 2 inches (50.8 mm) between a top of a backup tong gripper and a bottom of a torque wrench gripper, and the iron roughneck is configured to deliver up to 250 kNm of torsional force to the tubular string at a minimum vertical spacing.

Embodiment 27. The system of embodiment 26, wherein each of the actuator assemblies comprise:

the EX certifiable housing,

the electric motor contained within the EX certifiable housing, and

a linear actuator with a piston that extends or contracts in response to rotation of a coupling between the electric motor and the linear actuator, and

a structure attached to an end of the piston with a gripper attached to an opposite side of the structure from the piston, the gripper being configured to engage the tubular string when the piston is extended toward the tubular string.

Embodiment 28. A method for making or breaking a joint in a tubular string, the method comprising:

positioning the joint within a vertical opening that extends through an iron roughneck, with the iron roughneck comprising a torque wrench and a backup tong;

engaging the joint with the backup tong and the torque wrench, wherein an overall height of an engagement of the joint is less than 400 mm, and wherein the overall height is defined as a distance along the joint from a top of an engagement of the torque wrench to a bottom of an engagement of the backup tong; and

making or breaking the joint by rotating the torque wrench relative to the backup tong.

Embodiment 29. The method of embodiment 28, further comprising applying up to 250 kNm of torsional force to the joint via the torque wrench and the backup tong.

Embodiment 30. The method of embodiment 28, further comprising:

engaging the joint via first grippers in the torque wrench and second grippers in the backup tong; and

positioning the torque wrench adjacent the backup tong, such that grippers in the torque wrench are spaced away in a vertical direction from grippers in the backup tong by a vertical distance less than 60 mm.

Embodiment 31. The method of embodiment 30, operating an electric motor in a linear actuator assembly to extend or retract one of the first grippers or the second grippers toward or away from the joint.

Embodiment 32. The method of embodiment 30, wherein the iron roughneck comprises a linear actuator assembly for each one of the first grippers and the second grippers.

Embodiment 33. The method of embodiment 32, wherein the linear actuator assembly comprises:

an electric motor contained in an EX certifiable housing;

a linear actuator external to the EX certifiable housing, the linear actuator coupled to and driven by the electric motor, the linear actuator having a first axis and a body; and

a piston of the linear actuator that extends or retracts relative to the body when the linear actuator is driven by the electric motor, the piston having a second axis, with the first and second axes being parallel and spaced apart.

While the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and tables and have been described in detail herein. However, it should be understood that the embodiments are not intended to be limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the following appended claims. Further, although individual embodiments are discussed herein, the disclosure is intended to cover all combinations of these embodiments. 

1. A tool for conducting a subterranean operation, the tool comprising: a linear actuator assembly that comprises: an electric motor contained in an EX certifiable housing; a linear actuator external to the EX certifiable housing, wherein the linear actuator is coupled to and driven by the electric motor, and wherein the linear actuator includes a first axis and a body; and a piston of the linear actuator that extends or retracts relative to the body when the linear actuator is driven by the electric motor, the piston having a second axis, with the first axis and the second axis being parallel and spaced apart.
 2. The tool of claim 1, wherein the linear actuator is coupled to the electric motor via gears disposed in a fluid filled chamber.
 3. The tool of claim 2, wherein seals disposed between the EX certifiable housing and the fluid filled chamber prevent pressurized gas from entering the fluid filled chamber and prevent fluid from the fluid filled chamber from entering the EX certifiable housing.
 4. The tool of claim 1, wherein the EX certifiable housing receives pressurized gas through a gas inlet and exhausts the pressurized gas from the EX certifiable housing via a gas outlet, such that the pressurized gas in the EX certifiable housing is continually replaced with the pressurized gas received through the gas inlet.
 5. The tool of claim 1, wherein the linear actuator further comprises a structure mounted to an end of the piston, wherein the structure is configured to: engage a tubular, transfer a longitudinal force of the piston to the tubular, and direct a torsional force, applied to the tubular by the structure, away from the piston.
 6. The tool of claim 5, wherein the structure comprises a gripper that is removably attached to the structure, the gripper being configured to engage the tubular when the piston extends toward the tubular.
 7. The tool of claim 1, wherein the linear actuator assembly provides up to 700 kN clamping force when engaged with a tubular, and wherein a first overall volume includes the EX certifiable housing, the body of the linear actuator, and a gear box for coupling the linear actuator to the electric motor, and wherein the first overall volume is less than 32K cubic cm.
 8. The tool of claim 1, wherein the linear actuator assembly provides up to 700 kN clamping force when engaged with a tubular, and wherein a vertical height of the EX certifiable housing is less than 200 mm.
 9. A system for conducting a subterranean operation, the system comprising: an iron roughneck comprising a torque wrench having a plurality of actuator assemblies circumferentially positioned around an opening through the iron roughneck, wherein the opening is configured to receive a tubular string, and wherein each of the actuator assemblies comprise: an electric motor contained in an EX certifiable housing; a linear actuator with a piston that extends or contracts in response to rotation of a coupling between the electric motor and the linear actuator; and a structure attached to an end of the piston, the structure being configured to engage the tubular string with a gripper when the piston is extended toward the tubular string and transfer a torsional force away from the piston when the gripper is engaged with the tubular.
 10. The system of claim 9, wherein the torque wrench is configured to transfer up to 250 kNm of torsional force to the tubular string when the torque wrench is engaged with the tubular string.
 11. The system of claim 9, wherein each of the actuator assemblies is rigidly attached to a body of the torque wrench, and wherein the torque wrench is configured to transfer a torsional force to the tubular string when the torque wrench is engaged with the tubular string, and wherein the structure transfers the torsional force to the body of the torque wrench and away from the piston.
 12. The system of claim 9, wherein each of the actuator assemblies is rigidly attached to a body of the torque wrench, and wherein the torque wrench is configured to transfer a torsional force to the tubular string when the torque wrench is engaged with the tubular string, and wherein the structure comprises: a head portion; the gripper removably attached to the head portion; and a T-shaped protrusion that extends from the head portion, wherein the T-shaped protrusion is slidingly engaged with a groove in the body of the torque wrench, and wherein the groove is complimentarily shaped to receive the T-shaped protrusion.
 13. The system of claim 9, wherein the iron roughneck further comprises a backup tong spaced vertically away from the torque wrench, the backup tong having another plurality of the actuator assemblies circumferentially positioned around the opening in the iron roughneck.
 14. The system of claim 9, wherein the iron roughneck further comprises a backup tong spaced vertically away from the torque wrench, the backup tong having another plurality of the actuator assemblies circumferentially positioned around the opening in the iron roughneck, and wherein the iron roughneck is configured to produce a minimum vertical distance from a top of one of the grippers in the backup tong to a bottom of one of the grippers in the torque wrench, and wherein the minimum vertical distance is 60 mm (2.36 inches).
 15. The system of claim 14, wherein a maximum height from a top of the torque wrench to a bottom of the backup tong is less than 500 mm when the torque wrench is positioned adjacent the backup tong with the grippers in the backup tong being separated from the grippers in the torque wrench by the minimum vertical distance, with the maximum height including combined vertical heights of the backup tong, the torque wrench, and a vertical space between the backup tong and the torque wrench.
 16. The system of claim 15, wherein the torque wrench and backup tong are configured to transfer up to 250 kNm of torsional force to the tubular string when the torque wrench and the backup tong are engaged with the tubular string.
 17. A method for making or breaking a joint in a tubular string, the method comprising: positioning the joint within a vertical opening that extends through an iron roughneck, with the iron roughneck comprising a torque wrench and a backup tong; engaging the joint with the backup tong and the torque wrench, wherein an overall height of an engagement of the joint is less than 400 mm, and wherein the overall height is defined as a distance along the joint from a top of an engagement of the torque wrench to a bottom of an engagement of the backup tong; and making or breaking the joint by rotating the torque wrench relative to the backup tong.
 18. The method of claim 17, further comprising: engaging the joint via first grippers in the torque wrench and second grippers in the backup tong; and positioning the torque wrench adjacent the backup tong, such that grippers in the torque wrench are spaced away in a vertical direction from grippers in the backup tong by a vertical distance less than 60 mm; and applying up to 250 kNm of torsional force to the joint via the torque wrench and the backup tong.
 19. The method of claim 18, operating an electric motor in a linear actuator assembly to extend or retract one of the first grippers or the second grippers toward or away from the joint.
 20. The method of claim 18, wherein the iron roughneck comprises a linear actuator assembly for each one of the first grippers and the second grippers, and wherein the linear actuator assembly comprises: an electric motor contained in an EX certifiable housing; a linear actuator external to the EX certifiable housing, the linear actuator coupled to and driven by the electric motor, the linear actuator having a first axis and a body; and a piston of the linear actuator that extends or retracts relative to the body when the linear actuator is driven by the electric motor, the piston having a second axis, with the first and second axes being parallel and spaced apart. 